The use of compressors or superchargers is a well-known approach in order to increase the pressure and air density of air supplied to the internal combustion engine. The increased amount of air provides a greater amount of oxygen per engine cycle which in turn enables that the injected amount of fuel can be increased, resulting in that more power can be produced by the engine.
When the compressor clutch is engaged, the speed of the compressor is generally relatively low whereas the speed of the crankshaft that the compressor is engaged to is relatively high. Thus, there is a big difference between the speed of the crankshaft and the compressor. The larger the difference between the speed of the crankshaft and the speed of the compressor is when the compressor clutch is engaged, the larger is the amount of energy that instantly is transferred over the compressor clutch. High energy transfer during engaging of the compressor clutch causes high wear of the compressor clutch.
A typical approach in order to improve durability of the compressor clutch is to only allow engagement of the compressor clutch when the difference between the speed of the compressor and the speed of the crankshaft is within a limited range. This severely restricts the driving conditions where it is allowed to use the compressor.
For internal combustion engines provided with turbochargers also other aspects are important to consider when controlling the compressor. Since the air mass flow over the compressor highly affects the air mass flow to the subsequently provided turbocharger, it is important that the compressor do not stall the turbocharger. Hence, there is a need for an improved control method.